In recent years, various game systems in which characters are displayed in a simulated 3D space generated on a monitor screen have been spread. Some of such game systems are known to simulate skiing, surfing, motor-booting, snow boarding, skate boarding, etc.
Further, in order to make games more interesting as compared to those played in game systems which simulate running, sliding or like action on surfaces such as the ground surface and sea surface, there have been considered such simulated game systems that a character is caused to float from the ground surface, sea surface or other surface in a simulated 3D space on a monitor surface based on the undulation of the ground surface, sea surface or other surface and the running (or sliding) speed of the character. Typical games played in such game systems are snowboard games and half pipe games in which jumps are essential elements.
If a shadow of the character is thrown onto the ground surface, sea surface or other surface in such game systems in which the character is caused to float or jump in the simulated 3D space, a better presence can be given, thereby realizing game systems which can offer games having a variety of interesting and ingenious aspects.